1. Field of the Invention
The present invention relates to an etching apparatus and a method therefor, capable of performing low-pressure process etching.
2. Description of the Related Art
The most popular conventional dry etching apparatuses have parallel-plate electrodes, and RIE (Reactive Ion Etching) apparatuses and (Plasma Etching) apparatuses are known as such apparatuses. In either scheme, in order to generate a plasma with an etching gas and to maintain the plasma, the gas pressure in the etching chamber must be set to a comparatively high pressure of 100 mTorr or more. In etching in a comparatively high pressure atmosphere like this, a reaction by-product forms dust. Especially in a recent semiconductor device requiring micropatterning, the dust decreases the processing yield.
In an RIE dry etching apparatus, physical etching is mainly performed. Thus, high-energy ions of, e.g., 500 to 600 eV are incident on the wafer, leading to the damage to the semiconductor wafer.
In a PE dry etching apparatus, it is pointed out that although an etching shape dan be controlled comparatively easily, it is difficult to obtain a high etching rate.
In either scheme, the problem related to wafer damage caused by the ion energy of the reactive etching gas is conspicuous when the etching target is an oxide film, and the problem on destruction, of a gate oxide film and the like are particularly pointed out.
Recently, a magnetron RIE scheme is put into practice in which etching for micropatterning is performed by generating a high-density plasma in a comparatively low-pressure atmosphere. According to this scheme, however, electrons are locally present at wafer end portions in a direction perpendicular to the electric field and magnetic field, thereby causing a non-uniform plasma. Although rotation of the magnetic field and scanning are performed, a plasma is locally present on the wafer during a certain short period of time. This causes destruction of a gate oxide film constituting, e.g., a memory element. The problem on the destruction of the oxide film has not yet been effectively solved.